Acid anhydrides

ABSTRACT

Novel polyimides substituted by a substituent having an alkyl or fluoroalkyl group and having reduced water absorption; a process for producing these novel polyimides; and novel acid dianhydrides to be used in the production thereof. 
     A polyimide containing a structure represented by the following general formula (I):                    
     wherein X 1  represents a tetravalent organic group having a substituent —R 1 AR 2  (wherein A represents a divalent linkage group; R 1  represents a single bond or a C 1-3  alkylene group; and R 2  represents a C 1-25  alkyl group or a fluoroalkyl group); and Y represents a divalent organic group.

This application is a divisional of prior application Ser. No.09/604,116 filed Jun. 26, 2000 and now U.S. Par. No. 6,350,845.

FIELD OF THE INVENTION

This invention relates to novel polyimides, novel polyamic acids whichare intermediates thereof, a process for producing the same and novelacid dianhydrides to be used in the production of these novelpolyimides. More particularly, it relates to novel polyimides obtainedby introducing a monomer unit derived from acid dianhydrides substitutedby a substituent having an alkyl or fluoroalkyl group into the moleculeand these acid dianhydrides.

BACKGROUND OF THE INVENTION

Because of being excellent in heat resistance among various organicpolymers, polyimides have been widely used in the fields of, forexample, cosmology, aeronautics, electronic communication and officeautomation instruments. In recent years, there have been particularlyrequired polyimides which have not only a high heat resistance but alsovarious functions appropriate for uses.

In general, a polyimide has a relatively high water absorption due tothe large polarization between C═O and N in its imide ring. To improvethe existing polyimides, it is therefore one of the problems to besolved to reduce the water absorption.

As one of methods for reducing the water absorption of polyimides,JP-A-57-143329, JP-A-61-57620, JP-A-2-225522, JP-A-4-7333 andJP-A-4-100020 disclose a method of introducing alkyl and fluoroalkylgroups (the term “JP-A” as used herein means an “unexamined publishedJapanese patent application”). In this method, diamines having an alkylor fluoroalkyl group is used to thereby introduce these substituentsinto polyimides. However, there has been reported so far no polyimideobtained by introducing an alkyl or fluoroalkyl group into an aciddianhydride and then reacting it with a diamine. This is seeminglybecause there is known no acid dianhydride having an alkyl orfluoroalkyl group per se.

SUMMARY OF THE INVENTION

As the results of intensive studies, the present inventors have foundout acid dianhydrides carrying a substituent having alkyl or fluoroalkylgroup introduced thereinto and a process for producing novel polyimidesby using the same. The invention has been completed based on thesefindings.

The polyimide according to the invention is a polyimide containing astructure represented by the following general formula (I):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

DETAILED DESCRIPTION OF THE INVENTION

The term “organic group” as used herein means a group which is a part ofan organic compound and has linkage site(s) (the number of these linkagesites is expressed as valency). Aromatic groups and aliphatic groups mayfall within the category of the organic group. It is preferable that theorganic group has at least a part of its linkage sites on aromaticcarbon atom(s). Although the organic group is not particularlyrestricted in bulkiness, it typically carries from 15 to 74, preferablyfrom 19 to 59 and still preferably form 26 to 46, carbon atoms.

The term “linkage group” as used herein means a divalent functionalgroup which consists of, if necessary, hydrogen atom(s), carbon atom(s)and at least one heteroatom selected from among, for example, oxygen,nitrogen and sulfur atoms and has at least one of the linkage sites onthe hetero atom.

In one embodiment of the invention, A is an ester bond, an amide bond ora sulfonamide bond. An ester bond is a group formed by dehydratingcondensation of an oxo acid with an alcohol. For example, an ester bondof a carboxylic acid ester may be represented by —COO— or —OCO—. Thesame applies to other oxo acid esters. An amide bond may be representedby —NH—CO— or —CO—NH—. A sulfonamide bond may be represented by —NH—SO₂—or —SO₂—NH—.

In one embodiment of the invention, the polyimide is a copolymer havinga structure represented by the following general formula (II):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group);

X² is a tetravalent organic group different from X¹;

Y represents a divalent organic group;

m is an integer of 1 or more;

n is an integer of 0 or more; and

m/m+n is 0.01 or more; and

having an average molecular weight of from 5,000 to 1,000,000.

m and n represent respectively the numbers of imide units contained inthe copolymer molecule, while m/m+n represents the ratio of the imideunit having X¹. m preferably ranges from 1 to 100, n preferably ranges 0to 99 and m+n preferably ranges from 1 to 100. m/m+n preferably rangesfrom 0.01 to 1, still preferably form 0.1 to 1 and still preferably from0.2 to 1.

X¹, X² and Y may each occur in plural types in a polymer molecule.

The term “average molecular weight” as used herein means weight-averagemolecular weight measured by gel permeation chromatography (GPC). Itpreferably ranges from 3,000 to 1,000,000, still preferably from 10,000to 500,000 and still preferably from 20,000 to 300,000.

In one embodiment of the invention, X¹ is represented by the followinggeneral formula:

wherein

Z represents a divalent aromatic or aliphatic group having a substituent—R¹AR² (wherein A represents a divalent linkage group; R¹ represents asingle bond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkylgroup or a fluoroalkyl group); and

L is —O— or —NH—.

The term “aromatic group” means a group containing at least one aromaticring (for example, aryl, heteroaryl, arylalkyl). It carries typicallyfrom 15 to 74, preferably form 19 to 59 and still preferably from 26 to46, carbon atoms in total.

The term “aliphatic group” means a group having an aliphatic moiety butbeing free from aromatic rings. It carries typically from 1 to 60,preferably form 5 to 45 and still preferably from 12 to 32, carbonatoms.

In one embodiment of the invention, Z is represented by one of thefollowing general formulae:

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

The above general formulae representing Z all indicate that Z can linkat any two sites on the aromatic ring. It is preferable that p is from 1to 3.

In one embodiment of the invention, Z is —CH₂CH(COOR²)CH(COOR²)CH₂—,—CH₂CH(OCOR²)CH(OCOR²)CH₂—, —CH₂C(CH₂COOR²)₂CH₂—, —CH₂C(CH₂OCOR²)₂CH₂—,—CH(CH₂COOR²)CH(CH₂COOR²)—, —CH(CH₂COOR²)CH(CH₂OCOR²)— or—CH₂CH(CH₂COOR²)—,

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group.

The polyimide composition of the invention is a composition containingone of the polyimides as described above. This composition may containan arbitrary liquid or powder as a diluting medium wherein the polyimidecan be dissolved or uniformly dispersed.

The polyamic acid according to the invention contains a structurerepresented by the following general formula (III):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

In one embodiment of the invention, A is an ester bond, an amide bond ora sulfonamide bond.

In one embodiment of the invention, the polyamic acid is a copolymerhaving a structure represented by the following general formula (IV) ora structure represented by the following general formula (IV) whereinsome of the amic acid moiety has been dehydrated and condensed:

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group);

X² is a tetravalent organic group different from X¹;

Y represents a divalent organic group;

m is an integer of 1 or more;

n is an integer of 0 or more; and

m/m+n is 0.01 or more; and

having an average molecular weight of from 5,000 to 1,000,000.

In one embodiment of the invention, X¹ is represented by the followinggeneral formula:

wherein

Z represents a divalent aromatic or aliphatic group having a substituent—R¹AR² (wherein A represents a divalent linkage group; R¹ represents asingle bond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkylgroup or a fluoroalkyl group) and

L is —O— or —NH—.

In one embodiment of the invention, Z is represented by one of thefollowing general formulae:

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

In one embodiment of the invention, Z is —CH₂CH(COOR²)CH(COOR²)CH₂—,—CH₂CH(OCOR²)CH(OCOR²)CH₂—, —CH₂C(CH₂COOR²)₂CH₂—, —CH₂C(CH₂OCOR²)₂CH₂—,—CH(CH₂COOR²)CH(CH₂COOR²)—, —CH(CH₂COOR²)CH(CH₂OCOR²)— or—CH₂CH(CH₂COOR²)—,

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group.

The acid dianhydride according to the invention has a structurerepresented by the following general formula (V):

wherein

X¹ represents, a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group).

In one embodiment of the invention, A is an ester bond, an amide bond ora sulfonamide bond.

In one embodiment of the invention, X¹ is represented by the followinggeneral formula:

wherein

Z represents a divalent aromatic or aliphatic group having a substituent—R¹AR² (wherein A represents a divalent linkage group; R¹ represents asingle bond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkylgroup or a fluoroalkyl group); and

L is —O— or —NH—.

In one embodiment of the invention, Z is represented by one of thefollowing general formulae:

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

In one embodiment of the invention, Z is —CH₂CH(COOR²)CH(COOR²)CH₂—,—CH₂CH(OCOR²)CH(OCOR²)CH₂—, —CH₂C(CH₂COOR²)₂CH₂—, —CH₂C(CH₂OCOR²)₂CH₂—,—CH(CH₂COOR²)CH(CH₂COOR²)—, —CH(CH₂COOR²)CH(CH₂OCOR²)— or—CH₂CH(CH₂COOR²)—,

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group.

The process according to the invention is a process for producing apolyimide involving the step of reacting an acid dianhydride with adiamine, wherein the polyimide contains a structure represented by thefollowing general formula (I):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

The process according to the invention is a process for producing apolyamic acid involving the step of reacting an acid dianhydride with adiamine, wherein the polyamic acid contains a structure represented bythe following general formula (III):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

The process according to the invention is a process for producing anacid dianhydride involving the step of reacting a dihydroxybenzenederivative or a diaminobenzene derivative with an alkylating agent and atrimellitic acid anhydride derivative, wherein the acid dianhydride hasa structure represented by the following general formula (V):

wherein

X¹ is represented by the following general formula:

wherein

Z represents a divalent aromatic or aliphatic group having a substituent—R¹AR² (wherein A represents a divalent linkage group; R¹ represents asingle bond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkylgroup or a fluoroalkyl group); and

L represents —O— or —NH—.

The gist of the invention relating to the novel polyimides resides inthe acid dianhydrides substituted by a substituent having an alkyl orfluoroalkyl group and utilization thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The novel polyimide according to the invention is a polyimide containinga structure represented by the following general formula (I):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

The novel polyamic acid according to the invention is a polyamic acidcontaining a structure represented by the following general formula(III):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group); and

Y represents a divalent organic group.

The novel acid dianhydride according to the invention is an aciddianhydride having a structure represented by the following generalformula (V):

wherein

X¹ represents a tetravalent organic group having a substituent —R¹AR²(wherein A represents a divalent linkage group; R¹ represents a singlebond or a C₁₋₃ alkylene group; and R² represents a C₁₋₂₅ alkyl group ora fluoroalkyl group).

Next, embodiments of the novel polyimide according to the invention willbe described by reference to particular structural examples thereof.However, the polyimide is not particularly restricted in structure, solong as it is a polyimide composition having an alkyl or fluoroalkylgroup in a side chain of an acid dianhydride residue.

Particular examples of the process for producing the polyimide accordingto the invention include: 1) a process wherein an acid dianhydridehaving an alkyl or fluoroalkyl group is preliminarily synthesized andthen reacted with an arbitrary diamine to give a polyamic acid followedby cyclodehydration thereby giving a polyimide; and 2) a process wherein1 equivalent of an arbitrary diamine is reacted with 2 equivalents oftrimellitic acid anhydride chloride or with 2 equivalents of trimelliticacid anhydride in the presence of a condensing agent to give adicarboxylic acid which is then reacted with a diamine having an alkylor fluoroalkyl group thereby giving a polyimide.

First, illustration will be made on the process 1) wherein an aciddianhydride having an alkyl or fluoroalkyl group is preliminarilysynthesized and then reacted with an arbitrary diamine to give apolyamic acid followed by cyclodehydration thereby giving a polyimide.

As the acid dianhydride to be used as the starting material of the novelpolyimide of the general formula (I), use may be made of thoserepresented by the following general formulae (2-1), (2-2) and (2-3):

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

As the acid dianhydride to be used as the starting material of the novelpolyimide of the general formula (I), use may be also made of thoserepresented by the following general formulae (2-4), (2-5), (2-6) and(2-7):

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

As the acid dianhydride to be used as the starting material of the novelpolyimide of the general formula (I), use may be also made of thoserepresented by the following general formula (2-8):

wherein

Z′ is —CH₂CH(COOR²)CH(COOR²)CH₂—, —CH₂CH(OCOR²)CH(OCOR²)CH₂—,—CH₂C(CH₂COOR²)₂CH₂—, —CH₂C(CH₂OCOR²)₂CH₂—, —CH(CH₂COOR²)CH(CH₂COOR²)—or —CH(CH₂COOR²)CH(CH₂OCOR²)—.

As the acid dianhydride to be used as the starting material of the novelpolyimide of the general formula (I), use may be also made of thoserepresented by the following general formula (2-9):

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to 4.

Now, R¹ in the invention will be described. In case where thesubstituent —R¹AR² is attached to an aliphatic carbon atom, R¹ is asingle bond or an alkylene group, preferably a single bond or amethylene group. In case where the substituent —R¹AR² is attached to anaromatic carbon atom, R¹ is always defined as a single bond.

Next, R² in the invent ion (i.e., a C₁₋₂₅ alkyl or fluoroalkyl group)will be described. A C₁₋₂₅ alkyl group means a —C_(h)H_(2h+1) group(wherein h is from 1 to 25), while a C₁₋₂₅ fluoroalkyl group means a—C_(i)H_(j)F_(k) group (wherein i is form 1 to 25 and j+k is 2i+1).

With respect to the carbon atom number of t he alkyl or fluoroalkylgroup, a carbon atom number of a certain extent is needed to achieve alow water absorption. When the carbon atom number is too large, the aciddianhydride becomes hardly soluble in solvents which are used insynthesizing an amic acid serving as a precursor of the polyimide. Inthis case, the acid dianhydride becomes waxy and thus can be hardlyhandled. Thus, the carbon atom number available herein ranges from 1 to25, preferably from 3 to 20 and still preferably from 5 to 18.Preferable examples of the alkyl group include C₅₋₁₈ alkyl groups suchas hexyl, heptyl, octyl, nonyl and decyl groups.

In case where R² is a fluoroalkyl group —C_(i)H_(j)F_(k), k is 1 ormore, j is 0 or more and j+k preferably ranges from 3 to 51, morepreferably from 7 to 41 and most preferably from 11 to 37. Preferableexamples of the fluoroalkyl group include —CH₂CH₂(CF₂)₄CF₃ to—CH₂CH₂(CF₂)₁₄CF₃ and —(CF₂)₂CF₃ to —(CF₂)₁₆CF₃ having 1 to 25,preferably 3 to 20 and still preferably 5 to 18, carbon atoms.

Now, particular examples of the process for producing a novel aciddianhydride will be described.

First, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-1) as shown above will beillustrated.

An alkali metal (Li, Na, K, Rb, Cs, Fr) salt ofdihydroxybenzenecarboxylic acid is reacted with R²—Q′ (wherein Q′represents a halogen other than fluorine) in an aprotic polar solventunder heating to give (HO)₂—C₆H₃—COOR². This product is reacted with 2times by mol as much trimellitic acid anhydride chloride or with 2 timesby mol as much trimellitic acid anhydride in the presence of acondensing agent to thereby give a novel acid dianhydride represented bythe general formula (2-1). Compounds wherein p is from 2 to 4 can beobtained by substituting the dihydroxybenzenecarboxylic acidrespectively by dihydroxybenzenedicarboxylic acid,dihydroxybenzenetricarboxylic acid and dihydroxybenzenetetracarboxylicacid.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-2) will be illustrated.

(HO)₂—C₆H₃—NHCOR² can be obtained by reacting dihydroxyaminobenzene withR²COCl or with R²OOH in the presence of a condensing agent. Then thisproduct is reacted with 2 times by mol as much trimellitic acidanhydride chloride or with 2 times by mol as much trimellitic acidanhydride in the presence of a condensing agent to thereby give a novelacid dianhydride represented by the general formula (2-2). Compoundswherein p is from 2 to 4 can be obtained by substituting thedihydroxyaminobenzene respectively by dihydroxydiaminobenzene,dihydroxytriaminobenzene and dihydroxytetraaminobenzene.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-3) will be illustrated.

Compounds represented by the general formula (2-3) can be obtained as inthe case of the compounds of the general formula (2-2) but substitutingR²COCl by R²SO₂Cl.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-4) will be illustrated.

Novel acid dianhydrides represented by the general formula (2-4) can beobtained by reacting diaminodihydroxybenzene with 2 times by mol as muchtrimellitic acid chloride and then with R²COCl. Compounds wherein p isfrom 2 to 4 can be obtained by using diaminodihydroxybenzene,diaminotrihydroxybenzene and diaminotetrahydroxybenzene.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-5) will be illustrated.

An alkali metal (Li, Na, K, Rb, Cs, Fr) salt of diaminobenzenecarboxylicacid is reacted with R²—Q′ (wherein Q′ represents a halogen other thanfluorine) in an aprotic polar solvent under heating to give(H₂N)₂—C₆H₃—COOR². This product is reacted with 2 times by mol as muchtrimellitic acid anhydride chloride or with 2 times by mol as muchtrimellitic acid anhydride in the presence of a condensing agent tothereby give a novel acid dianhydride represented by the general formula(2-5). Compounds wherein p is from 2 to 4 can be obtained bysubstituting the diaminobenzenecarboxylic acid respectively bydiaminobenzenedicarboxylic acid, diaminobenzenetricarboxylic acid anddiaminobenzenetetracarboxylic acid.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-6) will be illustrated.

Novel acid dianhydrides represented by the general formula (2-6) can beobtained by reacting diaminobenzyl alcohol with 2 times by mol as muchtrimellitic acid chloride and then with R²COCl. Compounds wherein p isfrom 2 to 4 can be obtained by substituting the diaminobenzyl alcoholrespectively by (H₂N)₂C₆H₂(CH₂OH)₂, (H₂N)₂C₆H(CH₂OH)₃ and(H₂N)₂C₆(CH₂OH)₄.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-7) will be illustrated.

Compounds represented by the general formula (2-7) can be obtained as inthe case of the compounds of the general formula (2-6) but substitutingR²COCl by R²SO₂Cl.

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-8) will be illustrated.

HOCH₂CH(OH)CH₂—OCOR² can be obtained by reacting HOCH₂CH(OH)CH₂—Q(wherein Q represents a halogen) with an alkali metal salt of R²COOH inan aprotic polar solvent under heating. This product is reacted with 2times by mol as much trimellitic acid anhydride chloride or with 2 timesby mol as much trimellitic acid anhydride in the presence of acondensing agent to thereby give a novel acid dianhydride represented bythe general formula (2-8).

Next, an example of the process for producing novel acid dianhydridesrepresented by the general formula (2-9) will be illustrated.

(HOCH₂)₂C(CH₂OCOR²)₂ can be obtained by reacting, for example,(HOCH₂)₂C(CH₂Q)₂ (wherein Q represents a halogen) with an alkali metalsalt of R²COOH in an aprotic polar solvent under heating. This productis reacted with 2 times by mol as much trimellitic acid anhydridechloride or with 2 times by mol as much trimellitic acid anhydride inthe presence of a condensing agent to thereby give a novel aciddianhydride represented by the general formula (2-9). Acid dianhydrideshaving corresponding structures can be obtained by the same procedurebut substituting (HOCH₂)₂C(CH₂Q)₂ by HO—CH₂CHQCHQCH₂— OH orQCH₂CH(OH)CH(OH)CH₂Q.

Novel acid dianhydrides represented by the general formula (2-9) can beobtained by reacting an alkali metal salt of HOCH₂CH(COOH)CH(COOH)CH₂OH,HOCH₂C(CH₂COOH)₂CH₂OH or CH₂(COOH)CH(OH)CH(OH)CH₂(COOH) in an aproticpolar solvent under heating and then reacting this product with 2 timesby mol as much trimellitic acid anhydride chloride or with 2 times bymol as much trimellitic acid anhydride in the presence of a condensingagent.

The acid dianhydrides represented by the general formulae (2-1) to (2-9)obtained by the reactions as described above are examples which areparticularly useful as monomers of the novel polyimides. Other aciddianhydrides represented by the general formula (V) can be also obtainedin accordance with one of these processes with the combined use of knownstarting compounds and reactions.

Next, a process for synthesizing a polyimide via a polyamic acid will bedescribed by way of example.

A polyimide can be obtained by reacting a novel acid dianhydriderepresented by one of the general formulae (2-1) to (2-9) obtained abovewith a diamine in an organic polar solvent to give a polyamic acid andthen thermally or chemically imidating the polyamic acid.

In this reaction, either a single acid dianhydride or a mixture of twoor more acid dianhydrides may be used as the acid dianhydride.Similarly, either a single diamine or a mixture of two or more diaminesmay be used.

The term “thermally imidate” as used herein means a method wherein apolyamic acid is converted into a polyimide by merely heating.

The term “chemically imidate” as used herein means a method wherein adehydrating agent in a stoichiometric amount or more and a basiccatalyst are added to a polyamic acid polymer or its solution and thenimidataion is carried out by heating.

The dehydrating agent as used herein is exemplified by aliphatic acidanhydrides (for example, acetic anhydride) and aromatic acid anhydrides.The basic catalyst is exemplified by aliphatic tertiary amines (forexample, triethylamine), aromatic tertiary amines (for example,dimethylaniline) and heterocyclic tertiary amines (for example,pyridine, picoline, isoquinoline).

It is desirable that the polyamic acid has an average molecular weightof from 5,000 to 1,000,000. In case where it has an average molecularweight less than 5,000, the resultant polyimide has only a low molecularweight. It is undesirable to use this polyimide as such as aphotoreactive resin, since there arises an undesirable problem that theresin becomes brittle. It is also undesirable that the average molecularweight of the polyamic acid exceeds 1,000,000, since there arisesanother problem in this case that the polyamic acid varnish becomes tooviscous and shows poor handling properties.

Examples of the organic polar solvent to be used in the reaction ofproducing the polyamic acid include sulfoxide solvents (for example,dimethyl sulfoxide, diethyl sulfoxide), formamide solvents (for example,N,N-dimethylformamide, N,N-diethylformamide), acetamide solvents (forexample, N,N-dimethylacetamide, N,N-diethylacetamide), pyrrolidonesolvents (for example, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone),phenol solvents (for example, phenol, o-, m- or p-cresol, xylenol,halogenated phenols, catechol), hexamethylphosphoramide andγ-butyrolactone. Although it is desirable to use one of these solventsor a mixture thereof, it is also possible to use aromatic hydrocarbons(for example, xylene, toluene) as a part of the solvent.

To synthesize the polyimides having an alkyl or fluoroalkyl groupaccording to the invention, use can be made of the acid dianhydridesrepresented by the general formulae (2-1) to (2-9) of the inventiontogether with other acid dianhydrides, so long as the content of theacid dianhydrides represented by the general formulae (2-1) to (2-9) ofthe invention amounts to 1% or more of the total acid dianhydrides.

The other acid dianhydrides are not particularly restricted stricted solong as they are acid dianhydrides. For example, use may be madetherefor of aliphatic or alicyclic tetracarboxylic acid dianhydrides(for example, butanetetracarboxylic acid dianhydride,1,2,3,4-cyclobutanetetracarboxylic acid dianhydride,1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid,1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,2,3,5-tricarboxycylcopentylacetic acid dianhydride,3,5,6-tricarboxynorbonane-2-acetic acid dianhydride,2,3,4,5-tetrahydrofurantetracarboxylic acid dianhydride,5-(2,5-dioxotetrahydrofural)-3-methyl-3-cyclohexene-1,2-dicarboxylicacid dianhydride, bicyclo[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic aciddianhydride); aromatic tetracarboxylic acid dianhydrides (for example,pyromellitic acid dianhydride, 3,3′,4,4′-benzophenonetetracarboxylicacid dianhydride, 3,3′,4,4′-biphenylsulfonetetracarboxylic aciddianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride,2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3′,4,4′-biphenylether tetracarboxylic acid dianhydride,3,3′,4,4′-dimethyldiphenylsilanetetracarboxylic acid dianhydride,3,3′,4,4′-tetraphenylsilanetetracarboxylic acid dianhydride,1,2,3,4-furantetracarboxylic acid dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfide dianhydride,4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride, 4,4′-bis(3,4-dicarbophenoxy) diphenylpropane dianhydride,3,3′,4,4′-perfluoroisopropylidenediphthalic acid dianhydride,3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, bis(phthalic acid)phenylphosphine oxide dianhydride, p-pheneylene-bis(triphenylphthalicacid) dianhydride, m-phenylene-bis(triphenylphthalic acid) dianhydride,bis (triphenylphthalic acid)-4,4′-diphenyl ether dianhydride,bis(triphenylphthalic acid)-4,4′-diphenylmethane dianhydride);1,3,3a,4,5,6,9b-hexahydro-2,5-dioxo-3-furanyl)-naphth[1,2-c]furan-1,3-dione,1,3,3a,4,5,9b-hexahydro-5-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphth[1,2-c]furan-1,3-dioneand1,3,3a,4,5,9b-hexahydro-8-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphth[1,2-c]furan-1,3-dione.

Further examples of the acid dianhydrides usable herein includealiphatic tetracarboxylic acid dianhydrides having aromatic rings, forexample, compounds represented by the following general formula (3):

wherein Ra represents a divalent organic group having an aromatic ring;and Rb and Rc represent each a hydrogen atom or an alkyl group;

and compounds represented by the following general formula (4):

wherein Ra, Rb and Rc are each as defined above.

These acid dianhydrides may be used either alone or as a combination oftwo or more thereof.

As the diamine to be used in the polyimide, various diamines are usablein addition to diamines having a cinnamic acid skeleton. Arbitrarydiamines may be used without restriction. Examples thereof includearomatic diamines (for example, p-phenylenediamine, m-phenylenediamine,4,4′-diaminodiphenylmethane, 4,4-diaminophenylethane, 4,4′-diaminophenylether, 4,4′-didiaminophenyl sulfide, 4,4′-didiaminophenyl sulfone,1,5-diaminonaphthalene, 3,3-dimethyl-4,4′-diaminobiphenyl,5-amino-1-(4′-aminophenyl)-1,3,3-trimethylindan,6-amino-1-(4′-aminophenyl) 1,3,3-trimethylindan,4,4′-diaminobenzanilide, 3,5-diamino-3′-trifluoromethylbenzanilide,3,5-diamino-4′-trifluoromethylbenzanilide, 3,4′-diaminodiphenyl ether,2,7-diaminofluorene, 2,2-bis(4-aminophenyl)hexafluoropropane,4,4′-methylene-bis(2-chloroaniline),2,2′5,5′-tetrachloro-4,4′-diaminobiphenyl,2,2′-dichloro-4,4′-diamino-5,5′-dimethoxybiphenyl,3,3′-dimethoxy-4,4′-diaminobiphenyl,4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane,1,4-bis(4-aminophenoxy)benzene, 4,4′-bis (4-aminophenoxy)-biphenyl,1,3′-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene,4,4′-(p-phenyleneisopropylidene)bisaniline,4,4′-(m-phenyleneisopropylidene)bisaniline, 2,2′-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane,4,4′-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl);aromatic diamines having two amino groups bonded to an aromatic ring andhetero atom(s) other than the nitrogen atoms in these amino groups (forexample, diaminotetraphenylthiophene); and aliphatic diamines andalicyclic diamines (for example, 1,1-metaxylylenediamine,1,3-propanediamine, tetramethylenediamine, pentamethylenediamine,octamethylenediamine, nonamethylenediamine,4,4-diaminoheptamethylenediamine, 1,4-diaminocycloheaxne,isophoronediamine, tetrahydrodicyclopentadienylenediamine,hexahydro-4,7-methanoindanylenedimethylenediamine,tricyclo[6,2,1,02.7]-undecylenedimethyldiamine, 4,4′-methylenebis(cyclohexylamine)).

Further examples of the diamine usable herein include, for example,mono-substituted phenylenediamines represented by the following generalformula (5):

wherein Rd represents a divalent organic group selected from among —O—,—COO—, —OCO—, —CONH— and —CO—; and Re represents a monovalent organicgroup having a steroid skeleton;

and compounds represented by the following general formula:

wherein Rf represents a C₁₋₁₂ hydrocarbon group; y is an integer of from1 to 3; and z is an integer of from 1 to 20.

Further examples of the diamine include diamines having a photosensitivegroup, for example, 2′-(3,5-diaminobenzoate)-chalcone,7′-(3,5-diaminobenzoate)-coumarin, (3,5-diaminobenzoate)-cinnamic acid,coumarin-3-carboxylate-(3,5-diaminophenyl),coumarin-3-carboxylate-1-(3,5-diaminophenyl ester),1-(3,5-diaminophenoxy)-2-(cumarin-3-carboxylate)ethane,1-(3,5-diaminophenoxy)-2-(α-pyrone-5-carboxylate)ethane,3-(3,5-diaminobenzoate)-propionate-(2-chalcone),1-(3,5-diaminobenzoate)-2-(coumarin-3-carboxylate)ethane,1-(3,5-diaminophenyl)-coumarin-3-carboxamide, 3,5-diaminobenzylcinnamate, 3,5-diaminophenyl cinnamate,2-(2,4-diaminophenoxy)ethyl-1-cinnamate,2-(2,4-diaminophenoxy)ethyl-1-cinnamate, 2-(3,5-diaminobenzoicacid)propyl-1-cinnamate, (4′-aminophenyl)-4-aminocinnamate,(3-aminophenyl)-3-aminocinnamate,1′-amino-2′-naphthyl-(3-aminocinnamate), 1,3-bis(4-aminocinnamicacid)benzene and 1,2-bis(4-aminocinnaic acid)ethyl. Either one of thesediamine compounds or a combination of two or more thereof may be used.

Next, the process 2) wherein 1 equivalent of an arbitrary diamine isreacted with 2 equivalents of trimellitic acid anhydride chloride orwith 2 equivalents of trimellitic acid anhydride in the presence of acondensing agent to give a dicarboxylic acid which is then reacted witha diamine having an alkyl or fluoroalkyl group thereby giving apolyimide will be illustrated as another example of the process forproducing the polyimide according to the invention.

An arbitrary diamine (H₂N—Y—NH₂) is reacted with trimellitic acidanhydride and subjected to cyclodehydration to give a dicarboxylic acidrepresented by the following general formula:

wherein Y represents a divalent organic group.

Next, this dicarboxylic acid is reacted with a diol or a diaminerepresented by one of the following general formulae:

wherein Z represents —CH₂CH(COOR²)CH(COOR²)CH₂—,—CH₂CH(OCOR²)CH(OCOR²)CH₂—, —CH₂C(CH₂COOR²)₂CH₂—, —CH₂C(CH₂OCOR²)₂CH₂—,—CH(CH₂COOR²)CH(CH₂COOR²)— or —CH(CH₂COOR²)CH(CH₂OCOR²)—;

in the presence of a condensing agent to thereby give the desiredpolyimide having an alkyl or fluoroalkyl group.

The process for producing the polyimide according to the invention isnot restricted to the processes as described above. A polyimide havingan alkyl or fluoroalkyl group can be obtained by reacting 1 equivalentof diamines having an alkyl or fluoroalkyl group employed in thesynthesis of the acid dianhydrides of general formulas (2-5), (2-6) and(2-7) (or a mixture of these diamines with other arbitrary diamines)with 1 equivalent of trimellitic acid anhydride chloride or with 1equivalent of trimellitic acid anhydride in the presence of a condensingagent.

The polyimides according to the invention thus obtained may be mixedwith various organic additives or inorganic fillers or variousreinforcing agents to thereby provide compositions containing thepolyimides.

One of the characteristics of the novel polyimides of the inventionobtained by the above processes resides in having a low waterabsorption, which makes these polyimides appropriate for various uses.

The water absorption of the polyimides of the invention, measured inaccordance with ASTM D570 under the conditions as employed in Example 1,is typically 1.8% or less, preferably 1.5% or less.

Now, the invention will be described in greater detail by reference tothe following Examples. However, it is to be understood that theinvention is not construed as being limited thereto.

In the following Examples, ESDA means2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3′,4,4′-tetracarboxylic aciddianhydride; 6FDA means 2,2′-hexafluoropropylidenediphthalic aciddianhydride; BAPS-M means bis[4-(3-aminophenoxy)phenyl]sulfone; DMAcmeans N,N-dimethylacetamide; and DMF means N,N-dimethylformamide.

Weight-average molecular weight was measured by using GPC (manufacturedby Waters) under the following conditions: columns (2): KD-806Mmanufactured by Shodex, 60° C., detector: RI, flow rate: 1 ml/min,developing solvent: DMF (lithium bromide 0.03M, phosphoric acid 0.03 M),sample concentration: 0.2wt %, injection: 20 μl, standard: polyethyleneoxide.

Water absorption was measured in accordance with ASTM D570.

In the following Examples 1 to 9, acid dianhydrides according to theinvention and polyimides with the use thereof were produced.

EXAMPLE 1 Synthesis of 2,5-dihydroxybenzenecarboxylic Octane

1 mol of 2,5-dihydroxybenzoic acid and 0.5 mol of cesium carbonate wereadded to 200 ml of acetone and 200 ml of water and dissolved therein bystirring. After completely dissolving, the resultant solution wasconcentrated to dryness to give 1 mol of cesium 2,5-dihydroxybenzoate.85.8 g (0.3 mol) of cesium 2,5-dihydroxybenzoate, 57.9 g (0.3 mol) ofbromooctane and 300 ml of DMF were introduced into a reactor and reactedunder a nitrogen gas stream at 100° C. for 3 hours. The reactionsolution was concentrated, washed with water and dried to give 78 g(0.29 mol) of 2,5-dihydroxybenzenecarboxylic octane.

Synthesis of 2,5-(benzenecarboxylic octane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride

111.6 g (0.53mol) of trimellitic acid anhydride chloride and 600 ml oftoluene were introduced into a reactor and dissolved by stirring under anitrogen gas stream at about 70° C. 69.3 g (0.26 mol) of2,5-dihydroxybenzenecarboxylic octane and 50 g of pyridine weredissolved in 500 ml of toluene and the resultant solution was droppedinto the reactor as described above. After the completion of theaddition, the mixture was stirred and refluxed under nitrogen for about2 hours. After the completion of the reaction, the reactor wasice-cooled and the trimellitic acid anhydride chloride and pyridinehydrochloride thus precipitated were removed by filtration. The filtratewas concentrated and the solid matter thus obtained was recrystallizedfrom acetic anhydride to thereby give 120 g of 2,5-(benzenecarboxylicoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride.

The thus obtained compound was determined using a dimethyl sulfoxide-d₆(DMSO-d₆)/deuterochloroholm (CDCl₃) solvent by means of PMX60si NMRspectrometer (manufactured by LEOL LTD.).

(diol)

δ0.65-1.80 (m, —(CH₂)₆CH₃, 15H)

δ4.30 (t, COOCH₂—, 2H)

δ6.66-7.33 (m, Ph—H, 3H)

δ8.15 (s, OH, 1H)

δ10.20 (s, OH, 1H)

(Acid Dianhydride)

δ0.65-1.80 (m, —(CH₂)₆CH₃, 15H)

δ4.16 (t, COOCH₂—, 2H)

δ7.60-8.20 (m, Ph—H, 3H)

δ8.20-8.83 (m, Ph—H, 6H)

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 4.84 g (0.01 mol) ofthe acid dianhydride of Example 1 was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 8.2 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. The polyimide was dissolvedin DMF and cast on a PET film. After drying at 130° C. for 5 minutes,the PET film was stripped and drying was further effected at 150° C. for10 minutes to thereby give a film of 25 μm in thickness. This filmshowed a water absorption of 0.5%.

EXAMPLE 2

2,5-(Benzenecarboxylicnonadecafluorooctane)-dibenzoate-3,3′4,4′-tetracarboxylic aciddianhydride was obtained as in Example 1 but using Br-CH₂CH₂(CF₂)₇CF₃ asa substitute for bromooctane.

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 9.48 g (0.01 mol) ofthe acid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 13 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 0.4%.

EXAMPLE 3 Synthesis of 2,5-dihydroxybenzene-1,6-dicarboxylic Octane

0.5 mol of 2,5-dihydroxyterephthalic acid and 0.5 mol of cesiumcarbonate were added to 200 ml of acetone and 200 ml of water anddissolved therein by stirring. After completely dissolving, theresultant solution was concentrated to dryness to give 0.5 mol of cesium2,5-dihydroxyterephthalate. 46.2 g (0.1 mol) of cesium2,5-dihydroxyterephthalate, 38.62 g (0.2 mol) of bromooctane and 400 mlof DMF were introduced into a reactor and reacted under a nitrogen gasstream at 100° C. for 3 hours. The reaction solution was concentrated,washed with water and dried to give 40.1 g (0.95 mol) of2,5-dihydroxybenzene-1,6-dicarboxylic octane.

Synthesis of 2,5-(benzene-1,6-dicarboxylicoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic Acid Dianhydride:

35.8 g (0.17 mol) of trimellitic acid anhydride chloride and 200 ml oftoluene were introduced into a reactor and dissolved by stirring under anitrogen gas stream at about 70° C. 33.8 g (0.08 mol) of2,5-dihydroxybenzene-1,6-dicarboxylic octane and 16 g of pyridine weredissolved in 150 ml of toluene and the resultant solution was droppedinto the reactor as described above. After the completion of theaddition, the mixture was stirred and refluxed under nitrogen for about2 hours. After the completion of the reaction, the reactor wasice-cooled and the trimellitic acid anhydride chloride and pyridinehydrochloride thus precipitated were removed by filtration. The filtratewas concentrated and the solid matter thus obtained was recrystallizedfrom acetic anhydride to thereby give 38.5 g of2,5-(benzene-1,6-dicarboxylicoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride.

The thus obtained compound was determined using a dimethyl sulfoxide-d₆(DMSO-d₆)/deuterochloroholm (CDCl₃) solvent by means of PMX60si NMRspectrometer (manufactured by LEOL LTD.).

(Diol)

δ0.66-2.00 (m, —(CH₂)₆CH₃, 30H)

δ4.33 (t, COOCH₂—, 4H)

δ7.40 (s, Ph—H, 2H)

(Acid Dianhydride)

δ0.66-1.80 (m, —(CH₂)6CH₃, 30H)

δ4.20 (t, COOCH₂—, 4H)

δ8.00 (m, Ph—H, 2H)

δ8.10-8.90 (m, Ph—H, 6H)

4.32 g (0.01 mol) of BAPS-Mand 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 7.7 g (0.01 mol) of theacid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 11.2 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 0.3%.

EXAMPLE 4 Synthesis of 2,4-dihydroxybenzanilide Octane

37.5 g (0.3 mol) of2,4-dihydroxyaniline, 40.4 g (0.4 mol) oftriethylamine and 200 ml of water were introduced into a reactor andvigorously stirred under a nitrogen gas stream. 53.0 g (0.3 mol) ofpelargonic acid chloride was dissolved in 200 ml of THF(tetrahydrofuran) and the obtained solution was added to the reactionsolution as described above. After vigorously stirring, the THF layerwas separated by using a separating funnel, dehydrated over anhydrousmagnesium sulfate, concentrated to dryness and then purified byrecrystallization to thereby give 53.0 g of 2,4-dihydroxybenzanilideoctane. Synthesis of 2,4-(benzanilideoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride:

84.2 g (0.4 mol) of trimellitic acid anhydride chloride and 500 ml oftoluene were introduced into a reactor and dissolved by stirring under anitrogen gas stream at about 70° C. 53.0 g (0.2 mol) of2,4-dihydroxybenzanilide octane and 40 g of pyridine were dissolved in500 ml of toluene and the resultant solution was dropped into thereactor as described above. After the completion of the addition, themixture was stirred and refluxed under a nitrogen stream for about 2hours. After the completion of the reaction, the reactor was ice-cooledand the trimellitic acid anhydride chloride and pyridine hydrochloridethus precipitated were removed by filtration. The filtrate wasconcentrated and the solid matter thus obtained was recrystallized fromacetic anhydride to thereby give 74.0 g of 2,4-(benzanilideoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride.

4.32 g (0.01 mol) of BAPS-Mand 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 4.84 g (0.01 mol) ofthe acid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 8.5 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 70,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 0.9%.

EXAMPLE 5

2,4-(Amide octane benzsulfonate)-dibenzoate-3,3′,4,4′-tetracarboxylicacid dianhydride was obtained as in Example 4 but using octanesulfonicacid chloride as a substitute for the pelargonic acid chloride.

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 6.49 g (0.01 mol) ofthe acid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 10 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 0.9%.

EXAMPLE 6

3,5-(Benzenecarboxylic octane)-dibenzamide-3,3′,4,4′-tetracarboxylicacid dianhydride was obtained as in Example 1 but using3,5-diaminobenzoic acid as a substitute for the 2,5-dihydroxybenzoicacid.

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 6.1 g (0.01 mol) of theacid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 9.5 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 90,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 1.1%.

EXAMPLE 7

39.6g (0.2 mol) of3,5-dinitrobenzyl alcohol, 23.7 g (0.3 mol) ofpyridine and 200 ml of methyl ethyl ketone were introduced into areactor and dissolved by stirring under a nitrogen gas stream at about70° C. 35.3 g (0.2 mol) of pelargonic acid chloride was dissolved in 100ml of methyl ethyl ketone and the resultant solution was added dropwiseinto the reactor as described above. After the completion of theaddition, the mixture was refluxed and stirred under nitrogen for about2 hours. Then the reactor was cooled by allowing to stand and pyridinehydrochloride was removed by filtration. The filtrate was concentratedand purified by using a column to give 50.8 g of 3,5-dinitrobenzylpelargonate. 33.8 g of 3,5-dinitrobenzyl pelargonate and 4 g of acatalyst (5% palladium carried on active carbon) were introduced into ahydrogenation apparatus and reduced with hydrogen. After filtration andconcentration, 27.8 g (0.1 mol) of 3,5-diaminobenzyl pelargonate wasobtained.

42.1 g (0.2 mol) of trimellitic acid anhydride chloride and 300 ml ofmethyl ethyl ketone were introduced into a reactor and stirred withice-cooling under a nitrogen gas stream. 27.8 g (0.1 mol) of3,5-diaminobenzyl pelargonate and 23.7 g (0.3 mol) of pyridine weredissolved in 300 ml of methyl ethyl ketone and the obtained solution wasdropped into the reactor as described above. After the completion of theaddition, the mixture was stirred with ice-cooling under nitrogen forabout 2 hours and then refluxed and stirred for 2 hours. After thecompletion of the reaction, the reactor was ice-cooled and pyridinehydrochloride was removed by filtration. The filtrate was concentratedand the solid matter thus obtained was recrystallized from aceticanhydride to give 48 g of3,5-(benzyl-pelargonate)-diabenzamide-3,3′,4,4′-tetracarboxylic aciddianhydride.

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 6.3 g (0.01 mol) of theacid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAC were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 9.8 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 1.2%.

EXAMPLE 8

3,5-(Benzyl octanesulfonate)-dibenzamide-3,3′,4,4′-tetracarboxylic aciddianhydride was obtained as in Example 7 but using octanesulfonic acidchloride as a substitute for the pelargonic acid chloride.

4.32 g (0.01 mol) of BAPS-M and 30 g of DMAc were introduced into a 300ml separable flask provided with a stirrer. Then 6.2 g (0.01 mol) of theacid dianhydride of this Example was added at once thereto undervigorously stirring and stirring was continued as such for 30 minutes.0.93 g (0.02 mol) of β-picoline, 5 g of acetic anhydride and 10 g ofDMAc were added to the reaction solution and the resultant mixture washeated to about 120° C. for imidation. These reactions were carried outunder a nitrogen gas stream. After the completion of the reaction, thereaction mixture was poured into methanol, filtered and dried to therebygive 10 g of a yellow polyimide powder. This polyimide powder had aweight-average molecular weight of 80,000. A film was formed as inExample 1 and the water absorption was measured. As a result, this filmshowed a water absorption of 1.3%.

EXAMPLE 9

26.4 g (0.1 mol) of (3,5-diaminobenzoate)octane and 400 g of DMAc wereintroduced into a 2,000 ml separable flask provided with a stirrer. Then48.4 g (0.1 mol) of 2,5-(benzenecarboxylicoctane)-dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydridesynthesized in Example 1 was added at once thereto under vigorouslystirring and stirring was continued as such for 30 minutes. 9.3 g (0.2mol) of β-picoline, 50 g of acetic anhydride and 100 g of DMc were addedto the reaction solution and the resultant mixture was heated to about120° C. for imidation. These reactions were carried out under a nitrogengas stream. After the completion of the reaction, the reaction mixturewas poured into methanol, filtered and dried to thereby give 69 g of ayellow polyimide powder. This polyimide powder had a weight-averagemolecular weight of 100,000. A film was formed as in Example 1 and thewater absorption was measured. As a result, this film showed a waterabsorption of 0.2%.

Comparative Example 1

43.2 g (0.1 mol) of BAPS-Mand 160 g of DMAc were introduced into a 2,000ml separable flask provided with a stirrer. Then 21.8 g (0.1 mol) ofpyromellitic acid dianhydride was added at once thereto under vigorouslystirring and stirring was continued as such for 30 minutes to give apolyamic acid solution. 100 g of this polyamic acid solution was mixedwith 9.3 g (0.2 mol) of β-picoline, 20 g of acetic anhydride and 20 g ofDMAc and the obtained mixture was cast on an aluminum foil. After dryingat 100° C. for 2 minutes, the polyimide film was stripped from thealuminum foil and fixed in a pin frame. After drying at 200° C. for 2minutes, at 300° C. for 2 minutes and at 400° C. for 2 minutes, apolyimide film of 25 μm in thickness was obtained. Since the polyimidewas insoluble in solvents, it was impossible to measure theweight-average molecular weight thereof. This film showed a waterabsorption of 2.8%.

Comparative Example 2

26.4 g (0.1 mol) of (3,5-diaminobenzoate)octane and 400 g of DMAc wereintroduced into a 2,000 ml separable flask provided with a stirrer. Then21.8 g (0.1 mol) of pyromellitic acid dianhydride was added at oncethereto under vigorously stirring and stirring was continued as such for30 minutes to give a polyamic acid solution. 100 g of this polyamic acidsolution was mixed with 9.3 g (0.2 mol) of β-picoline, 20 g of aceticanhydride and 20 g of DMAc and the obtained mixture was cast on analuminum foil. After drying at 100° C. for 2 minutes, the polyimide filmwas stripped from the aluminum foil and fixed in a pin frame. Afterdrying at 200° C. for 2 minutes and at 300° C. for 2 minutes, apolyimide film of 25 μm in thickness was obtained. Since the polyimidewas insoluble in solvents, it was impossible to measure theweight-average molecular weight thereof. This film showed a waterabsorption of 2%.

The invention provides novel polyimides substituted by a substituenthaving an alkyl or fluoroalkyl group and having reduced waterabsorption. The invention further provides a process for producing thesenovel polyimides and novel acid dianhydrides to be used in theproduction thereof.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. An acid dianhydride having a structurerepresented by the following general formula (V):

wherein: X¹ is represented by the following general formula:

wherein Z represents a divalent aromatic group having a substituent—R¹AR² (wherein A is an ester bond, an amide bond or a sulfonamide bond;R¹ represents a single bond or a C₁₋₃ alkylene group; and R² representsa C₁₋₂₅ alkyl group or a fluoroalkyl group); and L is —O—.
 2. Thecompound as claimed in claim 1 wherein said Z is represented by one ofthe following general formulae:

wherein R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group; and pis from 1 to
 4. 3. A process for producing an acid dianhydride involvingthe step of reacting a dihydroxybenzene derivative with an alkylatingagent and trimellitic acid anhydride derivative, where said aciddianhydride contains a structural unit represented by the followinggeneral formula (V):

wherein X¹ is represented by the following general formula:

wherein Z represents a divalent aromatic group having a substituent—R¹AR² (wherein A represents C1 an ester bond, an amide bond or asulfonamide bond; R¹ represents a single bond or a C₁₋₃ alkylene group;and R² represents a C₁₋₂₅ alkyl group or a fluoroalkyl group); and Lrepresents —O—.